Public utilities and municipalities can save time and money on compaction controls

Public utilities and municipalities carry out compaction controls in pipe trenches to prevent embedded materials such as soil, sand, and crushed stone from causing settlements in the pavement surface after construction work. Often the controls are performed with conventional methods using an isotope gauge for measuring soil density and moisture content in the materials, supplemented with soil samples for reference measurements. However, often uncertainties are connected with the control values obtained. Other indirect methods such as measurements of bearing capacity, compaction applying light weight deflectometers (LWD) provide equally correct results – only faster and at a lower cost. In this context, Sweco offers training courses for utilities and municipalities in how to carry out fast, accurate compaction controls using a light weight deflectometer.

Facts

Customers: Public utilities/municipalities

Period: 2010–

Description

Pavement Consultants (Sweco's pavement consultancy department) produces light weight deflectometers applied for new constructions, maintenance of various types of pavement structures and, not least, for compaction controls in pipe trenches.

In 2010 the first compaction controls were carried out in pipe trenches using indirect methods, and these included the use of LWD. The project was carried out for Provas Haderslev Forsyningsservice A/S, and the utility still uses the deflectometer to this day whenever it carries out compaction controls in pipe trenches.

Before using the LWD, Provas, like many other utilities, used conventional methods of isotope probes and reference values. This meant that uncertainty was connected with the obtained control values. Soil samples were taken out for reference measurements and typically they had to wait up to two days for a laboratory reply. At the same time, the contractor's work on the project came to a standstill.

After Provas introduced the indirect methods as part of its compaction controls, the soil-sample results have been available right away. The contractor also saves time and money for reference measurements, which benefits the project.

At the request of five utilities in southern Jutland, Sweco has now held its first training course in how to carry out fast, accurate compaction controls using a LWD. The course is designed for utilities and municipalities and includes theoretical training which reviews the basis for carrying out compaction and the potential challenges posed by soil types, moisture content, substrata, etc. The practical part of the course is conducted in small groups, where the participants work with 1) the soil laboratory; 2) Troxler soil and moisture density gauges; 3) large falling weight deflectometers (FWD/HWD), light weight deflectometers (LWD) and calibration facilities; and 4) hands-on LWD training.

Please contact us if you would like further details about the course.

CUSTOMER QUOTES

"We have incorporated LWD measurements in our standard tender documents since 2010, as we use these measurements to test contractors’ compactions of pipe trenches. We are very satisfied with the method, especially because we are usually dealing with inhomogeneous materials and this means that we don’t need a new reference value every time, like we do when we use the isotope probe. The contractor gets the results right away and knows whether the compaction is approved or whether the compaction equipment needs to run through the pipe trench one more time. I definitely recommend other utilities and contractors to participate in similar training sessions. Sweco’s course was well organised with equal portions of hands-on and theoretical training, which generally covered all potential problems."
TOMMY SCHULTZ, PROJECT ENGINEER, PROVAS HADERSLEV FORSYNINGSSERVICE. Is very satisfied with using LWD measurements in his daily work and has participated in Sweco’s course.
"In my experience, many people don’t know enough about compaction control in general, which includes knowing the methods available for carrying out compaction control. For this reason, we encouraged Sweco to hold a day of training on compaction control in connection with construction projects where water and sewer lines are being laid in pipe trenches. The course attracted great interest, also from our colleagues at utilities in neighbouring municipalities. A total of 20 employees from five utilities in southern Jutland took part in a very well-organised and interesting day of training at Sweco in Kolding. I highly recommend the course, which would be excellent to hold for a mixture of participants from utilities and from municipal road departments, as they are the authorities for excavation works in roadways."
CHRISTOFFER HANSEN, PROJECT MANAGER, ARWOS. Helped plan the course contents.

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